public class Main {
    public static void main(String[] args) {
        //new一个对象
        Bus bus = new Bus();

        //调用Vehicle类
        bus.start();
        bus.speedUp(20);
        bus.stop();

        //调用Bus类
        bus.gotOn(5);
        bus.gotOn(3);
        bus.getOff(2);
        bus.getOff(7);
    }
}
